The present invention relates to a multi-speed automatic transmission installed in a vehicle or the like, and more specifically relates to an automatic transmission that includes first and second clutches disposed adjacent, wherein a clutch drum of the first clutch is pushed by hydraulic pressure or the like generated in a hydraulic servo of the second clutch.
Recent automatic transmissions installed in vehicles have been designed with more speeds, e.g. eight forward speeds and the like, to achieve better vehicle fuel efficiency and reduce emissions, and must also achieve a compact arrangement of many components including clutches from the standpoint of vehicle mountability.
A multi-speed automatic transmission requiring such compactness arranges two clutches (particularly the hydraulic servos thereof) adjacent to one another (see Japanese Patent Application Publication No. JP-A-2005-273768). The two clutches each have a friction plate formed from multiple discs and a hydraulic servo that pressably drives the friction plate. The hydraulic servos each include a piston, a hydraulic oil chamber that drives the piston, and a cancel oil chamber that cancels out a centrifugal oil pressure of the hydraulic chamber.